Dragonfire Ambusher

Megamorph {1}{r/g} (You may cast this card face down as a 2/2
creature for {3}. Turn it face up any time for its megamorph cost
and put a +1/+1 counter on it.)
Whenever Dragonfire Ambusher is turned face up, it may deal damage
to target creature equal to the number of +1/+1 counters on it.
Whenever you cast a creature spell, you may turn Dragonfire
Ambusher face-down.